Antibodies to nucleic acids are important diagnostically and pathogenetically in systemic lupus. Patients with active SLE have an increase in DNA in immune complexes. Such DNA is enriched in guanine (G) and cytosine (C). Low molecular weight DNA enriched in G-C is released from SLE leukocytes. This DNA may be important in the pathogenesis of SLE. Genes favoring the production of anti-DNA may include those which lead to the release of immunogenic DNA. In mice a subset of B cells is responsible for anti-DNA production. A similar human subset is being sought. If found, an attempt could be made to preferentially eliminate such B cells.